HP 5201L"Pulse Height Analyzer/Scaler-Timer (circa 1966)

[Dave92F1]

So... I picked up this thing for $50 on eBay. It's a HP 5201L "Pulse Height Analyzer/Scaler-Timer".



At first I was looking at it as a cheap source of nixies for a clock (or to gut the insides and turn the whole thing into a clock). But when I saw how nice it was - and that it appears to work (I think) - I'm tempted to try to restore it instead.

But I don't know exactly what it's meant to do. It seems to be some kind of nuclear research instrument; something to do with a scintillation detector. At a guess, I'd say it's a sort of counter with selectable count pre-scaler (the five digit wheels on the right), that counts pulses that exceed an adjustable trigger/threshold level (the knobs on the left). But that's just a guess. It's in the 1965 and 1969 HP catalogs, but they don't give much detail about what it does. I did find an ad for it here on the CERN server: https://cds.cern.ch/record/1728752/files/vol5-issue9-p137-e.pdf (see the last 3 pages of that PDF).

It appears to date from about 1966, based on the datecodes on the parts inside. I don't have a manual or schematic.

I powered it up and it seems to run - the nixies light up, the knobs change the status of the lights, etc.

I was going to fiddle with it to figure out exactly what it can do, but after running about 5 minutes, smoke (!) started coming from one board that seems to be part of the power supply. So I shut it off (before anything failed).

More pictures follow. Suggestions/advice/guesses/data/etc. invited!

Back panel:



Top view inside:



(BTW, if anybody has pinouts/data for the Nixie modules, that'd be really great.)

Bottom view inside (before blowing dust out of it):



Two boards pulled out (to check the burning one):



Close up of the board that was smoking (note 2 orange resistors on the left):

[DTJ]

I think I remember correctly but I could be wrong..........

 This can be used for identifying radioactive sources.

The input is a window comparator. The knobs on the left adjust the upper and lower thresholds (in eV). The output of the comparator goes to a counter timer.

If I remember correctly when radioactive decay occurs the energy of the emission (particle or gamma) can define the material. By adjusting the comparator slot up and down and taking counts over a fixed period you can work out the different energy peak(s) for a radioactive material. Using the energy value for the peaks and the relative heights of the peaks you can look at tables and work out what is in your sample. Books like the CRC handbook of chem & physics have all the data tables needed.

I used a Single Channel Analyser (the comparator part) and a separate counter timer instrument 30+ years ago in a uni physics lab experiment where we had to ID different samples.

[Someone]

As above its a component of a basic gamma spectroscopy apparatus that requires an appropriate scintillator and detector (typically PMT):
https://en.wikipedia.org/wiki/Gamma_spectroscopy

With appropriate "standards" (physical examples to calibrate against) it is possible to determine the (relative) composition of an unknown sample, but it is most sensitive to strong gamma emitters and is largely useless outside of a radionuclide laboratory. Modern techniques would be recording all the pulses coming from the detector and binning them into a histogram (multichannel analyser) so they can be seen in the context of the background noise.

[joeqsmith]

I like the looks of old equipment like this.  Would make a good looking desk clock...

[Dave92F1]

Thanks, everyone! Those explanations make sense.

Given that something's wrong with it (indicated by smoke after 5 min), probably I'll try to reverse engineer how the Nixie modules work and then gut the rest of the innards.

I thought it'd make a nice clock, too. (But it is kind of large for a desk clock.)

BTW, did anybody notice how the 3 momentary push buttons on the front panel are constructed? Have another look:



That's what I call doing it the old-fashioned way.

[DTJ]

Rack mount it into your bed head. It's a chick magnet! 

[crazyguy]

Rack mount it into your bed head. It's a chick magnet! 

perform the radiation survey first, maybe the PHA is contaminated by radioactive substance

[TheSteve]

Nice bit of kit. While it's very pretty inside I would have no hesitation gutting it for a nixie clock.

[Cubdriver]

So you wound up getting that.  I had been watching it, but was put off by the expensive shipping cost.  I'd start by checking the filter caps - one may be shorted if things smoked like that.

I personally would try to get it working again rather than gutting it to make a clock (Russian Nixie tubes are readily available for that), but then I'm not quite right in the head and collect old stuff like this.

-Pat

[Dave92F1]

So you wound up getting that.

I'm local to the seller, so I just drove over and picked it up. (Otherwise I wouldn't have paid the shipping either.)

I think I've convinced myself to gut the insides (but keep the outside). As a packrat and admirer of fine engineering, it takes intestinal fortitude to do it, but I think I'm up for it.

[Dave92F1]

Rack mount it into your bed head. It's a chick magnet! 

Don't we all wish the world worked that way?

[Dave92F1]

It's been 6 years. So maybe I'm ready to do something on this.

Anybody have a schematic/manual for this thing (HP 5201L)?

I paid a guy on eBay $20 for a manual, but it turns out he didn't really have one (did get my $ back...).

[factory]

BAMA have the 5233L manual which covers the 5233L-65D PSU board, look for the others by the board number, as some are used in multiple counters. There will of course be some unique parts to this model.

Alternately if you want to sell it, I'm sure a few of us would be interested, myself included.

David